Two self-anointed "grammar vigilantes" who toured the nation removing typos from public signs have been banned from national parks after vandalizing a historic marker at the Grand Canyon.

Jeff Michael Deck, 28, of Somerville, Mass., and Benjamin Douglas Herson, 28, of Virginia Beach, Va., pleaded guilty in U.S. District Court in Flagstaff after damaging a rare, hand-painted sign in Grand Canyon National Park. They were sentenced to a year's probation, during which they cannot enter any national park, and were ordered to pay restitution.

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Deck's diary account of the Grand Canyon incident was submitted as evidence in court. It says the two men climbed Desert View Watchtower while on holiday from their typo-enforcement duties "and discovered a hand-rendered sign inside that, I regret to report, had a few errors. I know today was supposed to be my day off from typo-hunting, but if I may be permitted to quote that most revered of android law enforcers, Inspector Gadget, 'Always on duty!' I can't shut it off. . . . Will we never be free from the shackles of apostrophic misunderstanding, even in a place surrounded by natural beauty?"

After correcting a misplaced apostrophe and comma, Deck reported, he was aghast to discover what he described as a made-up word: "emense."

"I was reluctant to disfigure the sign any further, so we had to let the other typo stand. Still, I think I shall be haunted by that perversity."